WASHINGTON (AP) — Citing a potential threat to public health, the Food and Drug Administration is taking steps toward phasing out the use of some antibiotics in animals processed for meat.

Many cattle, hog and poultry producers give their animals antibiotics regularly to ensure that they are healthy and to make the animals grow faster. Now, the agency has announced that it will ask pharmaceutical companies to voluntarily stop labeling drugs important for treating human infection as acceptable for that growth promotion in animals.

If the drug companies sign on — and two major companies have already signaled they will — using those antibiotics to promote growth in animals would be illegal. Prescriptions would be required to use the drugs for animal illnesses.

The FDA has been debating how to address the issue of antibiotics in meat for several years as antibiotic-resistant diseases have risen and consumers increasingly have clamored for antibiotic-free meat. McDonald’s, among other companies, has moved to limit the drugs in their meat, pushing many animal producers to go along. The restaurant chain Chipotle also has tried to use meat raised without antibiotics, but has cited challenges in finding enough of it.

FDA officials said the move is designed to limit antibiotic-resistant diseases in humans as antibiotic resistance has become a growing public health problem. Repeated exposure to antibiotics can lead germs to become resistant to the drug so that it is no longer effective in treating a particular illness.

In September, the Centers for Disease Control and Prevention released sobering estimates that more than 23,000 people a year are dying from drug-resistant infections.

The biggest risk is from germs spread in hospitals, and it’s not clear how much of the problem is related to the use of drugs in meat. Still, the FDA says this is one step toward decreasing resistance.

“We need to be selective about the drugs we use in animals and when we use them,” said William Flynn of FDA’s Center for Veterinary Medicine. “Antimicrobial resistance may not be completely preventable, but we need to do what we can to slow it down.”

The new guidance will give the companies three years to comply.

Michael Taylor, FDA’s deputy commissioner of foods, said he believes asking industry to make the changes is the fastest way to help phase the drugs out. If the FDA made the process mandatory, he said, the agency would have had to move forward with a complex regulatory process that could take years.

“We have high confidence based on dialogue with industry that this initiative will succeed,” Taylor said.

Drug companies Zoetis and Elanco, two of the leading manufacturers of animal antibiotics, have signaled they will comply.

The American Academy of Pediatrics said the move will be particularly helpful for children, who already are limited in the number of antibiotics they can take.

“When one type of antibiotic is found to be resistant to a strain of an infection, some of our sickest young patients are left without life-saving treatment options,” said Thomas K. McInerny, the group’s president.

Animal agriculture groups will not have much of a choice in the matter if drug companies sign on and make the drugs’ use illegal. But many antibiotics will still be available for those producers to use, just not those that the FDA has classified as most important for treating human infections. Some of the antibiotics that could not be used in animals are penicillins and tetracyclines, the FDA said.

Many animal groups signaled support for the FDA guidance after it was announced Wednesday, including the National Pork Producers Council. Still, Dr. Liz Wagstrom of the pork producers’ group said the FDA action will mean “real change” in the way antibiotics are used on the farm, as some animals may not grow as quickly and producers may see more disease. She said she does not know how much it will cost the industry.

Some advocates pushing to rid the animal food supply of antibiotics said the FDA did not go far enough. Democratic Rep. Louise Slaughter of New York, a microbiologist, said the FDA should have made the action mandatory. The guidance “falls woefully short of what is needed to address a public health crisis,” she said.

Others hailed the agency move as progress.

“We commend FDA for taking the first steps since 1977 to broadly reduce antibiotic overuse in livestock,” said Laura Rogers of The Pew Charitable Trusts’ human health and industrial farming campaign. “There is more work to do, but this is a promising start, especially after decades of inaction.”